1. Field of the Invention
The present invention relates to a fluorine-based compound containing a polar group and a pertluoroalkylene group, and a lubricant composition including the same. More specifically, the present invention relates to a lubricant composition which is useful as a lubricant for a recording medium such as a magnetic disk, a magnetic tape, and the like as a mass-storage recording medium. In addition, the present invention relates to various uses of the lubricant composition, and specifically to a film and a laminate having the film, a magnetic recording medium, a head slider, and a magnetic recording device, each of which is formed using the lubricant composition.
2. Background Art
A thin film type magnetic recording medium is produced by forming a magnetic layer formed of a ferromagnetic metal or an alloy thereof on a nonmagnetic substrate by means of various methods (for example, a sputtering method, a vapor deposition method, a non-electrolytic plating method, and the like). When the magnetic recording medium is practically used, it is brought into contact with a magnetic head at a high speed, so the medium suffers from abrasion damage or is caused to have deterioration in the magnetic characteristics in some cases. Accordingly, a protective film and a lubricating layer are provided on the magnetic layer so as to improve the abrasion resistance. A carbonaceous film has been generally used as a material of the protective film layer. In addition, a fluorine-based compound is generally used as a material of the lubricating layer.
In this way, the lubricating layer of the recording medium is very useful for the purpose of reducing the abrasion damage and the deterioration of magnetic characteristics caused by the contact that occurs between the head and the medium, by means of reducing a coefficient of kinetic friction. On the other hand, particularly, when the film thickness of the lubricating layer is large, the head floating becomes unstable due to attachment of the lubricating layer to a head or interaction between the lubricant and the head, and thus, there is a concern about occurrence of errors during the read-write or a crash with a disk. On the other hand, if the film thickness of the lubricating layer is reduced, the above phenomenon does not easily occur, but the function of the lubricating layer, that is, the suppression of the abrasion damage and deterioration of the magnetic characteristics caused by the contact between the head and the disk cannot be accomplished in some cases. In order to increase the surface recording density, it is required to keep the floating height of the head low and speed up the disk rotation, and thus, it is important to maintain the function of the lubricating layer.
Accordingly, various attempts for solving the above problem by carefully selecting a lubricant that is used for the lubricating layer have been made. In JP-A-2010-248463 discloses a fluorine-based compound having a predetermined structure containing a cyclic group, a polar group directly bonded to an aromatic ring, and a fluorine-based chain, and a lubricant composition including the same, but the adsorptive force with respect to a substrate and the shape of a coated surface are not always satisfactory. Accordingly, a further improvement in this is demanded.
Furthermore, various lubricant compositions using a polymer that includes a mesogen structure in a main chain or a side chain, and grease compositions have been proposed (for example, JP-A-2006-307202 and JP-A-2008-195799), but whether these compositions are useful as materials used for the lubricating layer for a recording medium has not been clarified.